You had mentioned pairing with Challenge? Whats advantage of that appose to full RPI system.

Thanks Cal!

If you pair the RPI GTM axle back unit with Challenge X-Pipes, you have multiple options depending on what setup you want to go with. (ie: retain OEM cats, utilize HFCs, catless w/ resonators, etc.) whereas the full RPI GTM race system is just catless with no resonators...